Computational analysis of polymer molecular structure effect on nanocavities replication via injection moulding

The purpose of this work is to study how the molecular structure of a polymer affects the replication of nanocavities when injection moulding manufacturing process is used. Even though the process and geometrical factors that affect the replication of nanocavities have been studied by several authors, the effect of the polymer molecular structure on the injection result is less studied. In order to study through simulation the molecular structure influence, Computational Fluid Dynamics methods are not valid because they consider the matter a continuum. This limitation is overcome by means of Molecular Dynamics simulation method, in which each atom movement is tracked in a sort of n-body problem. With a self-made model, the effect of degree of polymerization and tacticity are successfully quantified in the replication of nanocavities of down to 2·2nm². It is concluded that the degree of polymerization has a negative effect on the nanocavity replication due to the easier entanglement of longer polymer chains. Concerning the tacticity effect, it is found out that syndiotactic polystyrene replicates less than atactic or isotactic polystyrenes because of the larger entanglement of the phenyl groups when in alternate positions along the chain.